DE2804616A1 - METHOD AND DEVICE FOR PYROLYTIC DEGRADATION OF AN ORGANIC MATERIAL - Google Patents

Description

DR.-INS. DIPL-ING. M. SC 3IPL - PHVS. Γ Π. DIPL.-PHYS.

HÖGER - LEGAL RIGHTS - GRiESSBACH - HAECKER

PATENT LAWYERS IN STUTTGART

A 42 704 b Applicant: Beringer Co., Inc.

k - 163 Beringer Way

January 30, 1978 Marblehead, Mass. 01945

United States

description

Method and device for the pyrolytic degradation of an organic material

The invention relates to a method for pyrolytic degradation an organic material, in particular a plastic material, and a device for performing the method .

In particular, the invention is concerned with processes for the pyrolytic separation of polymeric organic compounds of objects or substances which are essentially not influenced by the temperatures to be used. Such Processes are useful in the plastics industry to remove various plastics from objects such as molds, Spray heads, baffles, sieves and filters, multi-hole spinning heads, Extruder screws, pumps, nozzles and other similar Remove tools or components.

It is important that the cleaned elements can be used again. Procedures of the type under consideration are also useful when it comes to recovering metal parts from associated polymers or plastics to separate, where appropriate, components of the plastics can also be recovered.

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Numerous methods are known with the aid of which plastics or plastic layers are removed from metal parts can be. With the exception of those processes involving solvents or ultrasonic cleaning equipment or both are used, temperatures between about 427 and about 482 ° C, at which the plastics disintegrate. During this disintegration, volatile constituents are formed, which in general are combustible while leaving a residue, which is often predominantly carbon. When in heat treatment Oxygen is present, then the carbon oxidizes, leaving an inorganic dust or powder as the residue remains behind.

The previously known cleaning methods include, for example covering the parts with molten salt, heating the parts in an oven, in air, in an inert gas or in steam, dipping the parts in a bed of heated alumina and heating the parts with a Cutting torch or on a hot plate. Each of these known methods has one or more disadvantages. For example the salt or, more generally, the material in which the parts to be cleaned are immersed must be regularly replaced will. In addition, there is air pollution from smoke and / or vapors. The cleaning takes a considerable amount Time to complete; the parts from which the plastic is to be removed are annealed and / or deformed; it there are dangers for the operating personnel if the molten salt splashes out of its containers, boils over or like; Salt remains on the metal parts

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or aluminum oxide, which requires further cleaning do; there are restrictions on the type and quantity of plastics that can be removed, and there are restrictions on the proper cleaning of parts which have complicated shapes.

Many of the disadvantages listed above are avoided by the special process of vacuum pyrolysis, which in the journal "SPE Journal" July, 1973, Volume 29, Page 25 in the article "Now: Remove Plastic Deposits from Extruder parts the modern way "is described. According to this process, plastic-coated or soiled Parts introduced into a chamber which is equipped with radiant heaters and to which a vacuum pump is assigned, which leads to an exhaust pipe. The parts are heated under negative pressure. When temperatures are between about 427 and 482 C. are reached, the plastic material breaks down, with certain Evaporate constituents, the vapors of which are drawn off through a condensate trap, where most of the solids condense, if they come into contact with water. The vapors and water leaving the condensate trap enter into the vacuum pump. The water and vapors are transported from the pump to another separator where the water is drained or returned to the vacuum pump, while the vapors pass through a vent chimney either directly or via a gas-heated afterburner into the atmosphere.

In the development of this procedure, a

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second chamber under negative pressure or worked with a collecting vessel installed under the first chamber and was connected to it via a connecting pipe. In doing so, the second chamber was on an essential basis lower temperature than the first chamber. When heating up are now in the first chamber at increased Temperature certain plastics flow and fall into a collecting container, which is connected to the second via the connecting pipe Chamber where the temperature is low enough to cause resolidification. The second chamber had a drip pan and a door that could be removed of the collected plastic material. With this embodiment of the method indicated above, a considerable Part of the plastic material can be recovered without to be pyrolytically degraded.

In some cases, however, difficulties arose with the design of the earlier method as described, since the Molten plastic material did not flow out of the vacuum chamber quickly enough to cause pyrolytic degradation to prevent rising temperature. This difficulty was primarily due to the toughness of the melted Plastic material, which hindered its drainage and in many cases led to a blockage of the connecting pipe. Attempts have been made to overcome this problem by providing the connecting pipe with a heater which was only partially successful.

Based on the state of the art, the object of the invention is to be found

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based on improving the removal of the molten polymeric material from the heated vacuum chamber so that this Material can be effectively collected and resolidified without any significant pyrolytic degradation he follows.

This object is achieved according to the invention by a method of type described at the beginning, which is characterized by the following features:

(a) Enclose the material in a first enclosed space;

(b) a negative pressure is created in the space;

(c) the room is heated to a temperature in a first temperature range which is sufficient to achieve the To bring material to melt without it being degraded to a significant extent, so that part of the Material from the first room can freely fall into a second room that is connected to it a much lower temperature is kept, so that the part of the material falling into it is kept can solidify again, and

(d) the material remaining in the first space is heated to a temperature within a second temperature range elevated temperature sufficient to thermally degrade the material, with the volatile components peeled off, so that only an ash-like residue remains.

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The inventive method offers the advantage that only the parts of the material that have not flowed off when heated to the temperature in the first temperature range and that are in the generally make up only a fraction of the total material, then pyrolytically decomposed at an elevated temperature are, while the remaining part of the material, in particular the plastic material, after resolidification from the cooler second chamber can be removed.

The method according to the invention can be designed in such a way that after the evaporation of the volatile components the residue, if it has a high carbon content, is further burned or oxidized with a supply of air, so that a dusty or powdery residue results, which essentially consists only of inorganic pigments or Fillers that can be easily removed from the treated parts.

Details and advantages of the method according to the invention are explained in more detail below with reference to a drawing, the single figure of which shows a preferred embodiment of a device shows for carrying out the method according to the invention.

In the drawing, reference numeral 12 denotes a chamber arrangement, which is designed in three parts and in which a negative pressure can be generated. The chamber assembly 12 has a first Chamber 14, a second chamber or a collecting vessel 16 and a connecting part 18, which is preferably, but not necessarily, through a vertical pipe, considerable diameter

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knife is formed, as described below v / ird. The first chamber 14 is preferably lined with stainless steel, insulated and with one or more electrical Radiant heaters 20 equipped. In addition, there is a temperature sensor (not shown), a grate 22, a door 24 for inserting or removing the grate 22 and a collecting container 26 provided. The collecting container 26 has a centrally arranged outlet opening 28, which is aligned with the longitudinal axis of the connecting part 18 is aligned so that molten plastic flowing out of the collecting container 26 is free can fall down without touching the walls of the connecting part and thereby to a mass 30 of solidified or Once again solidified plastic arrives in the collecting vessel 16.

The connecting part 18 has such dimensions and is oriented so that it thermally away from the collecting vessel 16 first chamber 14 isolated so that the temperature in the collecting vessel 16 is considerably below that in the first chamber 14 lies. This enables the plastic to solidify immediately after it has reached the collecting vessel 16. The collecting vessel 16 has a door 32 for removing the solidified plastic at the end of a working cycle.

The first chamber 14 is preferably provided with devices (not shown) which enable the grate 22 to be positioned outside of the chamber 14 to be loaded with parts to which plastic adheres, / also made it possible to then the loaded grate 22 to be inserted into chamber 14. In addition, an air valve 33 is provided, the purpose of which will be explained below.

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A pipe 36 leads to one. Condensate see id he 38 or /. one Water spray chamber in which a nozzle 40 is provided, the is connected to a water source and with the help of which a spray 41 can be generated. The spray hits the Vapors that get from the first chamber 14 into the condensate separator 38.

Another pipeline leads from the condensate separator 38 to a vacuum pump 44, which is designed as a water ring pump is. An arrow 46 indicates that the vacuum pump 44 is still water from a recirculation tank 48, on the bottom is discussed in more detail, can be supplied.

A pipe 50 connects the vacuum pump 44 with a separator 52, which has a water bag in which the water, which carries trapped polymer particles is separated from the remaining gases. The water runs through a pipe 54 to the recirculation tank 48, while the gases are fed via a pipe 56 to a gas-operated afterburner 58 will. Its exhaust gases are fed to a chimney 60. In many cases the afterburner 58 can be omitted if the concentration of pollutants in the vapors in the pipe 56 below that required by the local authorities Limits lies.

A source of make-up water is connected to the tank 48 via a valve 62. The tank 48 is constructed in a conventional manner and serves to filter out plastic particles trapped by the water, while the purified water, as through indicated by the arrow 46, fed back to the vacuum pump 44

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will. Suitable devices are provided to clean the tank 48 at certain intervals. The valve 62 is only opened when it is necessary to supply additional water in order to replace a corresponding amount of water which was drained off via a line 64 with a siphon. The amount of water drained is controlled so that the temperature of the water returned to the vacuum pump 44 remains below about 30 ° C. It has been shown that the effectiveness of the vacuum pump 44 is improved at water temperatures below the specified upper limit.

If desired, in the system, preferably in the closed loop between the vacuum pump 44 and skimmers, fine sieves or other filters can be used in the tank 48.

It is also possible to discharge the waste water directly from the separator 52 and to do without the tank 48, when recirculation of the water is not required.

The device described above can be operated in different ways, which are explained below. The operating mode selected in the individual case depends on the type and quantity of the plastic material to be subjected to pyrolysis. The plastics differ in two important features, namely in their ability to operate at one temperature to melt, which is below the temperature at which a noticeable deterioration occurs, and in their property, after at least extensive evaporation of all its volatile constituents, a residue with a high carbon

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to form salary. For example, vinyl and rubber compounds cannot be liquefied to such an extent that they are flowable at temperatures at which the compounds mentioned do not yet decompose. Many other compounds, on the other hand, are flowable at temperatures below the temperatures at which decomposition begins. These include, for example, polystyrene, polyolefin, polycarbonate , nylon, polyester and polypropylene compounds, to name just a few of the best-known examples. Some polymers, such as the polyolefins and polystyrenes, do not have a high carbon residue after their volatiles have evaporated, while other polymers such as the polyester, nylon, vinyl, polycarbonate, and rubber compounds leave such a residue.

In operation, the device under consideration can be regulated manually, but is preferably by means of an automatic one Timer (not shown) regulated in order to automatically adapt to the during automatic operating cycles typical properties of the respective plastic or Polymer and the amounts of the same to be removed from the parts 34. A duty cycle generally has a duration between 60 and 90 minutes, but may take longer in some cases.

The following description is generalized to include various Capture types of commonly used plastics. In the case of the individual plastics, the duration is every Treatment step, the level of the maintained negative pressure and the temperature in the individual parts of the chamber

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arrangement appropriately set for optimal effectiveness, cleanliness of residues and speed of the To achieve plastic removal.

When working with the device shown in the drawing, the first are the soiled or coated with plastic Parts 34 placed on the grate 22 in the first chamber 14, whereupon the doors 24 and 32 are then sealed will. In addition, the air valve 33 is closed. Afterward the vacuum pump 44 is then turned on to operate in the closed chamber assembly 12, tube 36 and the condensate scrubber 38 to generate a negative pressure. Typically, a vacuum of between about 635 and 686 mm Hg is maintained. At the same time, one or more radiant heaters 20 are switched on in order to increase the temperature in the first Chamber 14 to initiate.

At a given temperature, some of the aforementioned plastics melt from the parts 34 dripping down onto the inclined bottom of the collecting container 26 and flow off through its outlet opening 28. The material then falls through the connecting part 18 into the much cooler collecting vessel 16, where it solidifies as a mass 30. The chambers 16 and 16 and the connecting part 18 are arranged so that the The temperature in the collecting vessel 16 preferably does not rise above a maximum value of approximately 66 ° C. during a working cycle The temperature in the first chamber 14, on the other hand, rises to significantly higher values, as will be explained below. Man recognizes that due to the fact that the collecting container 26 is in the heated first chamber 14, the in

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the collecting container 26 dripping plastic material in the remains essentially at the same temperature until it drips off through the outlet opening 28. After passing the exhaust port 28-does the plastic at no point come into contact with a wall area of the "connecting style 18 and" falls under the influence of gravity freely through this connecting part into the cooler collecting vessel 16.

Due to the described configuration of the chamber arrangement 12, the plastic material melting down from the parts 34 in the chamber 14 is discharged very quickly, as a result of which it becomes clogged of pipes and ducts is avoided and thereby also prevents the plastic from being in the first chamber is held back that it begins to disintegrate with increasing temperature in the same.

The at least one radiant heater 20 continues to be supplied with energy in order to increase the temperature in the first chamber 14 until the plastic residues on the parts 34 begin to disintegrate and thereby release volatile constituents. This thermal decomposition of the plastic is not accompanied by a combustion process, since there is a lack of oxygen in the chamber 14. Usually the temperatures required for vaporizing are between about 427 and 482 C, while the device is preferably designed so that it can reach temperatures up to:
can be.

operated at temperatures of about 538 ° C in chamber 14

Those emanating from the parts 34 during the decomposition of the plastics Vapors enter the condensate via pipe 36

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Scheider 38, where they are detected by the spray 41. Almost all of the vapors are in the condensate separator 38 entrained solid particles are precipitated by the water. The water loaded with the solids passes together with the remaining vapors the vacuum pump 44 and reaches the separator 52. From the separator 52 are almost all vapors are fed via conduit 56 to afterburner 58 where all combustible components can be burned. In practice, the afterburner 58 is not normally required because the vapors in the conduit 56 are sufficient are clean so that they can be discharged directly into the atmosphere.

The water with the solids passes through the pipe 54 to the tank 48, where essentially all of the solids are filtered out while the remaining water is returned to the vacuum pump 44.

The amount of water that is drained off via the pipe 64 containing the siphon is essentially equal to the amount of water, which flows through nozzle 40 and valve 62, thereby keeping the temperature of the returned water below about 30 ° C v / ird.

After a certain period of time, all of the vaporizable components of the plastic - these components are common combustible - leave the first chamber 14, v / o a residue remains on the parts 34. In certain cases it has Residue has a high carbon content. For example, the residue from polyester compounds contains about 86% carbon.

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While the chamber 14 is held at a temperature between about 427 and 482 C and the vacuum pump 44 is running, the negative pressure is gradually reduced or equalized to atmospheric pressure by using the air valve 33 air can flow in, with the help of which the carbon can be burned to carbon monoxide or carbon dioxide. For improvement of the reaction conditions, the air supplied via the air valve 33 can be preheated, and it can also Devices can be provided which distribute the air evenly over the parts 34. Those created during the combustion process Gases are drawn off through the pipe 36 and pass into the condensate separator 38. The after combustion on the Parts 34 remaining residues are generally dusty or powdery and exist for the most part from inorganic pigments and fillers. As soon as this state has occurred, the radiant heater 20 and the vacuum pump 44 switched off and the door 24 opened to remove the parts 34.

It goes without saying that the above-described step of supplying air via the air valve 33 is omitted in certain cases can, for example, if the polymer or plastic is a polyvinyl chloride compound and if it It is desirable to prevent hydrochloric acid gas from being released during combustion.

The final cleaning of the parts can be carried out using any known method, for example with With the help of a jet of air, by wiping or by blasting with glass, wood flour, lime or soda particles under low Pressure.

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Although in the device described above, a chamber arrangement 12 with a vertical connecting part x 18 can be used to carry out the described method Structurally modified devices can also be used. For example, a single chamber can be provided whose The interior is divided into two superimposed areas by a heat shield. The upper range can in this case contain the grate and the collecting container 2 6 for the melted Plastic material and the radiant heater (s). The heat shield may have an opening through which the molten plastic freely falls into the lower cooler area of the chamber. The heat shield can with reflective surfaces be provided, through which the thermal radiation is reflected upwards in the direction of the parts located on the grate will.

The method described above has been used with success to convert plastics from parts with complicated shapes remove. In particular, with the method according to the invention, the removal of plastics is possible without the parts affected by it warp or their surface quality deteriorates significantly.

Furthermore, it has been shown that the process is safe for workers and provides good control of wastewater quality and of air pollution.

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Claims (8)

DR.-ING. DIPL.-ING. M. SC DIPL. PHYS. ο.!. DIPL.-PHYS. HÖGER - LEGAL RIGHTS - GRIESSBACH - HAECKER PATENT LAWYERS IN STUTTGART A 42 704 b Applicant: Beringer Co., Inc. k - 163 Beringer Way January 30, 1978 Marblehead, Mass. 01945 United States Patent claims: Method for the pyrolytic degradation of an organic material, in particular a plastic material, characterized through the following features: (a) Enclose the material in a first enclosed space; (b) a negative pressure is created in the space; (c) the room is heated to a temperature lying in a first temperature range which is sufficient to bring the material to melt without it being degraded to any significant extent, so that some of the material from the first room is freely into a associated second space can fall, which is kept at a much lower temperature, so that the part of the material falling into it can solidify again _r and (d) the material remaining in the first space is heated to one in a second temperature range lying elevated temperature that is sufficient 809849/0567 A 42 704 b k - 163 Jan. 30, 1978 - 2 - 280461B in order to thermally degrade the material, the volatile components being drawn off, so that only an ash-like residue remains. 2. The method according to claim 1, characterized in that the removed volatile components and solid particles contained therein in a water spray chamber treated. 3. The method according to claim 1, characterized in that subsequent to the removal of the volatile components and while maintaining the temperature lying in the second temperature range, air into the first space initiates so that the carbon in the residue is burned with the oxygen in the air to form gaseous oxides, which are withdrawn from the first space, where an essentially inorganic residue remains. 4. The method according to claim 3, characterized in that one entrained by the stream of gaseous oxides Separates solid particles in water. 5. The method according to claim 1, characterized in that there is a temperature for the first temperature range chooses between about 427 and 477 C. 6. The method according to claim 1, characterized in that the first and the second space with each other combines that the falling part of the material does not come into contact with wall areas. 809849/0567 A 42 704 b _ January 30, 1978 - 3 - 7. Device for performing the method according to a of claims 1 to 6, characterized in that a chamber arrangement (12) with a heatable first chamber (14) and one below it in terms of temperature against the first chamber (14) shielded second Chamber (16) is provided that the two chambers (14, 16) are connected to one another and can be closed in a sealing manner that a vacuum pump (44) is provided, with the help of which in the chamber arrangement (12) a negative pressure can be generated, and that in the connecting line (36, 42) between the negative pressure pump (44) and the Chamber arrangement (12) a condensate separator (38) is provided. 8. Apparatus according to claim 7, characterized in that the first chamber (14) has a connection (33) for supplying air. 809849/0567